The present invention relates to the field of topography, and, more particularly, to an automated method and related system for making topographical models.
Topographical models of geographical areas may be used for many applications. For example, topographical models may be used in flight simulators and for planning military missions. Furthermore, topographical models of man-made structures (e.g., cities) may be extremely helpful in applications such as cellular antenna placement, urban planning, disaster preparedness and analysis, and mapping, for example.
Various types and methods for making topographical models are presently being used. One common topographical model is the digital elevation map (DEM). A DEM is a sampled matrix representation of a geographical area which may be generated in an automated fashion by a computer. In a DEM, co-ordinate points are made to correspond with a height value. DEMs are typically used for modeling terrain where the transitions between different elevations (e.g., valleys, mountains, etc.) are generally smooth from one to a next. That is, DEMs typically model terrain as a plurality of curved surfaces and any discontinuities therebetween are thus xe2x80x9csmoothedxe2x80x9d over. For this reason, DEMs generally are not well suited for modeling man-made structures, such as skyscrapers in a downtown area, with sufficient accuracy for many of the above applications.
U.S. Pat. No. 6,104,981 to Louis et al. is directed to a method for assisting the detection of man-made structures in a DEM. The method includes computing isolines from a completed DEM, filtering the isolines based upon size criterion, computing extremum isolines from the filtered isolines, and isolating regions of interest, including man-made structures, from regions delimited by the extremum isolines. Even though this method may assist in distinguishing manmade structures once a DEM is rendered, the accuracy of the structures in the DEM is still limited by the curve fitting used to make the DEM.
Another approach to producing topographical models has been developed by the Harris Corporation, assignee of the present invention, and is commercially referred to as RealSite(trademark). RealSite(trademark) provides a semi-automated process for making three-dimensional (3D) topographical models of geographical areas, including cities, that have accurate textures and structure boundaries. Moreover, RealSite(trademark) models are geospatially accurate. That is, the location of any given point within the model corresponds to an actual location in the geographical area with very high accuracy (e.g., within a few meters). The data used to generate RealSite(trademark) models may include aerial and satellite photography, electro-optical, infrared, and light detection and ranging (LIDAR).
RealSite(trademark) models not only provide enhanced accuracy over prior automated methods (such as automated DEM generation), but since they are produced using a semi-automated computer process they may be created much more rapidly than comparable manually rendered models. Yet, even though the RealSite(trademark) model generation process begins with actual data of a geographic location, some user delineation is required to distinguish objects within an input data set before automated computer algorithms can render the final models. Thus, producing RealSite(trademark) models for large geometric areas of several kilometers, for example, may require a significant amount of time and labor.
In view of the foregoing background, it is therefore an object of the invention to provide an automated method and related system for making a topographical model of an area including terrain and buildings thereon relatively quickly and with enhanced accuracy.
This and other objects, features, and advantages in accordance with the present invention are provided by an automated method for making a topographical model of an area including terrain and buildings thereon based upon randomly spaced data of elevation versus position. The method may include processing the randomly spaced data to generate gridded data of elevation versus position conforming to a predetermined position grid, processing the gridded data to distinguish building data from terrain data, and performing polygon extraction for the building data to make the topographical model of the area including terrain and buildings thereon.
More specifically, the randomly spaced data may include light detection and ranging (LIDAR) data, for example. Processing the randomly spaced data may include resampling the randomly spaced data based upon a polynomial fit of predetermined order. The polynomial fit of predetermined order may include at least one of an average, a tilted plane, a biquadratic, a bicubic, and a biquartic, for example. The randomly spaced data is preferably resampled using a lowest order polynomial fit for a predetermined accuracy. Further, resampling preferably uses substantially all of the randomly spaced data.
Additionally, processing the gridded data may include processing the gridded data using a plurality of position windows to distinguish the building data from the terrain data. The method may also include processing the gridded data to distinguish small features from the buildings and terrain.
Performing polygon extraction may include determining boundaries for each building based upon the building data, determining vertices of the boundaries for each building, and using the vertices to define polygons for each building. Furthermore, the boundaries for each building may be smoothed prior to determining vertices of the boundaries. The method may also include merging scaled optical images of the buildings onto the respective buildings of the topographical model as well as assigning at least one of a color and an intensity to the buildings and terrain of the topographical model based upon respective elevations thereof.
A system according to the invention is for making a topographical model of an area including terrain and buildings thereon based upon randomly spaced data of elevation versus position. The system may include a collector for collecting the randomly spaced data, a processor for receiving the randomly spaced data from the collector and making the topographical model of the area including terrain and buildings thereon, and a display connected to the processor for displaying the topographical model. The processor may make the topographical model by processing the randomly spaced data to generate gridded data of elevation versus position conforming to a predetermined position grid, processing the gridded data to distinguish building data from terrain data, and performing polygon extraction for the building data.
A computer readable medium having computer-executable instructions thereon is also provided for causing a computer to make a topographical model of an area including terrain and buildings thereon based upon randomly spaced data of elevation versus position. The instructions cause the computer to make the topographical model by performing the steps of processing randomly spaced data to generate gridded data of elevation versus position conforming to a predetermined position grid, processing the gridded data to distinguish building data from terrain data, and performing polygon extraction for the building data to make the topographical model of the area including terrain and buildings thereon.